Copy and Paste Poses not working
You should check Mirroring.


  If you want to mirror your animation form the left side to the other
  side during pose mode you just need to select the whole left side then
  copy the pose with Ctrl+C.





  After that press Ctrl+i to go to your right side
  and finally press Shift+Ctrl+V to
  paste the the X flipped pose, that way you'll have a perfect mirror of
  both side




Or enable X Axis Mirror option.